Process for obtaining phenols from coal tar distillates



Sept. 1, y R.lcRoss 1,820,908 l PROCESS FOR OBTAINING PHENOLS FROM COAL TAR DIS'IIILLATES Filed May 2, 1925 Fece/iev' Fey/ux rea/v;

-latenlzedD Sept. 1,1931

.ROY CROSS, 0F KANSAS CITY, MISSOURI PROCESS Fon. OBTAINING PHENoLs FROM COAL TAR DrsrILLATEs Application filed May 2, 1925. serial No. 27,491.'

This invention relates to improvements in coal tar phenols and related compounds and a process of making the same, and refers more particularly to the production of coal tar phenols such as cresylic acid including such materials as meta-creso-l, para-cresol and ortho-cresol and related compounds by the thermal decomposition of the coal tarv and its heavier' distillates 'at high temperatures and pressures.

Among'the objects of the invention are, to provide a product and process in which is produced, by cracking or thermal decomposition,cresylic acid having a germicidal value greater than phenol and a product readily recovered vby dissolving material from the distillate and recovered by neutralization of the solvent vehicle; to provide a product,l which, besides having a high germicidal value, is commercially important as a basis for dye stuffs, and, in general, to provide a product and process hereinafter described in more detail.

The single figure is a diagrammatic side elevational view of an apparatus adaptable for producing coal tarphenols of the character described.

Referring to the drawing, l is a furnace v containing the preheating coil 2 and the heating coil 3. 4 is a reaction chamber; 5 is an evaporator;l6 is a bubble tower; 7 is a condenser, and 8 is a receiver. Unvaporized material withdrawn from the evaporator is reduced in temperature in a cooler 9 prior to being directed to storage.

Describing, briefly, the operation, the coaltar distillate to be treated is introduced through the charging line 10, controlled by a valve 11, and is forced by means of a pump 12 through a line 13, thence through the continuous coils 2 and 3 where it is brought to a cracking tempera-ture and directed through the discharge line 14 to the reaction chamber 4. During its passage through the heating coils and reaction chamber, it is preferably maintained under cracking conditions of temperature and pressure controlled to effect cracking without substantial vaporization of the material being treated. Ou discharge from the reaction chamber, pressure is reduced at the valve 15 and the highly heated products are discharged into the evaporator 5 where the volatile fractions pass ot'f through the vapor line 16, while the unvaporized material is drawn off either continuously or intermittently through the line 17, controlled by the valve 18, which conducts the unvaporized products to the cooler 9 where, after cooling in the coil 19, the products are directed to storage through the o discharge line 20. The overhead volatile material is subjected to a refluxing action in, the dephlegmator 6, Which is preferably of the bubble tower construction in order to more effectively separate out the fractions having a higher boiling range than those desired in the final distillate. The uncondensed vapors passing off from the top of the bubble tower are directed through the line 2l to the condenser coil 22 positioned in the condenser 7 and passed nally into the receiver 8 where they are collected as liquid distillate. This receiver is equipped with a liquid draw off line 23, regulated by a valve 24, and a gas line 25, controlled by a valve 26. The condensed or refiuXed material collected in the bottom of the bubble to'wer is drawn off through the line 27, controlled by the valve 28, returned to be recycled with the charging stock by means of the pump 12. An auxiliary charging line 29, controlled by a valve 30, is connected into the line 11 for the purpose of supplying products containing the hydroxyl group such as glycols', glycerols and alcohol. With certain coal tars. it has been found advantageous to supply material of this character in order to increase the yield of phenols or cresylic acid in the final distillate A bypass line 31, around thereaction chamber and controlled by valves 32 and 33, furnishes a means for cutting out the reaction chamber when it is desired to operate under lower pressure and effect the conversion by pressure distillation'- as contrasted with the conversion described in which Athe cracking takes place without substantial vaporizatiou or under excessive pressures preferably in excess of 350 pounds per square inch. The

cracking of the'coal tar distillates includes pressures ranging from 50 to 1,000 pounds per square inch and temperatures of from 750 Ff. to 1,000 F. Normally, it has been found advantageous to operate at temperatures of from 800 F. to 950F. during the reaction' period and at pressures of from 600 to 1,000 pounds per square inch.

In the case of typical German coal tar having a specific gravity of 1.101 yielding an overhead distillate having a specific gravity of 1.007, this latter distillate utilized asA charging stock and representing approximately one-half of the original coal tar,l on being subjected to temperatures of 850 F. and 600 pounds pressure per square inch,

. resulted in a synthetic producty having substantially thirtyv (30%) percent of cresols or cresylic acid soluble in caustic s oda'and approximately thirty 30%) percent of aromatic hydrocarbons. The specific gravity of a mixed product distilled'from the synthetic oil at temperatures up to 437 F. had a speci- .ic gravity of 0.891, and initial boiling pointof .125 lF., While the cresols or portions of the product soluble in caustic soda solution had a specific gravity of 1.03. The specific l* preferably done as described by passing the charging stock through a` coil in a furnace into an expansion chamber or reaction chamber as shown at 4 in the drawings. Distillation subsequent to this cracking reaction may be eitherdirect from the expansion chamber which may be carried onv in the apparatus shown by by-passing the reaction chamber and utilizing the evaporator as the expansion chamber or the pressure may be reduced land distillation carried on from the-expansion chamber 5 by a reduction of pressure between the reaction chamber and the evaporator,- the chamber 4 being used solely as the reaction stage. The heavy residue, as: described, may be continuously or intermittently removed as pitch `from the evaporator and a portion of the distillate, passing over at a higher temperature than 440 F. or thereabouts, is returned by refluxing to be retreated in a heating stage. As mentioned, it has also been found that the yield of phenols or cresols or their allied products may be increased by the addition of substances con taining the hydroxyl group such as glycols1 glycerols and alcohols. The largest yield is obtained from heavy coal tar which has beenl slightly oxidized or made from coal carrying considerable oxygen. Itis probable that the v droxylgroups.

rezagos single plant by continuous operation Without redistillation or reheating to produce a Water- Wliite cresylic acid or cresols of mixed composition.

The phenols or cresols, as described, are products of thermal decomposition which are substantially insoluble in Water and soluble ina caustic soda solution; further, they have a specific gravity of at least one, and a normal distillation range of approximately 350. to 450 F. The coal tar phenols consists of the benzene nucleus with one or more hy- Phenols and their related compounds, produced as described, have a ,f g'ermicidal- Vahle greater than commercial.

phenol or carbolic acid as produced at.tl1e present time and `according to the germicidal table issued by the United Statesl-Iygienic Laboratory under the Treasury Department, lVashington, D. C.

To recover the-phenols from the distillate, the latter is treated with a caustic soda solution which dissolves out the phenol, the latter' being recovered by neutralization of the solvent vehicle With acid such as hydrochloric and sulphuric.

Besides being produced from coa-l tar compounds such as hereinbefore explained, phenols and their related products including cresylic acid and the like, may be produced as a by-produet from certain petroleum hydrocarbons containing aromatic compounds or a benzene nuclensf-a typical oil being an oil ofy California. type. 'hen petroleum hydrocarbons are treated for their phenol content, t-he eresylic acid products would be byproducts of a light motor fuel produced and recovered from the linal distillate b 'v dissolving out this material with a caustic soda solution similarly to thev treatment of coal tar distillate. d y \A I claim as my invention: i 1. A process of producing coal tar phenols' comprising the steps of adding an alcohol to a. coal tar distillate, 'alul then subjecting the distillate to cracking teinperatln'es and pressures, condensing the evolved vapors, collecting the distillates, and recovering the phenols therefrom. y

2. A process of producing coal tar phenols, comprising the steps of subject-ing a coal tar distillate to cracking temperatures and pressures regulated to prevent material vapori- Zation, releasing the pressure and distilling oft' the volatile fractions with the contained .heat of the oil, condensing the vaporized materia-l and' recovering the phenols.

3. A process of producing coal tar phenols, comprising the steps of subjecting coal tar distillate to temperatures ranging from 700 F. to 1000o F. and pressures in excess of 350 pounds per square inch, releasing the pressures and distilling oli' the volatile fraction, condensing the vaporized material and recovering the phenols' OY CROSS R 

